1. Field of the Invention
This invention relates to Striped Magnetoresistive (SMR) heads and Dual Stripe Magnetoresistive (DSMR) heads and more particularly to methods of manufacturing of exchange biasing configurations therefor, as well as devices manufactured by such methods.
2. Description of Related Art
As the continuous trend in magnetic recording requires increased areal density, track widths of magnetic recording heads are being reduced. Commonly assigned U.S. patent application Ser. No. 09/182,775, filed Oct. 30, 1998 of Yimin Guo et al. for xe2x80x9cAnti-Parallel Longitudinal Patterned Exchange Biased Dual Stripe Magnetoresistive (DSMR) Sensor Element and Method for Fabrication Thereofxe2x80x9d describes a narrow track width DSMR head with dual sensors. The head, which increases signal amplitude is stabilized by anti-parallel biasing, i.e. with biasing which is parallel, but in the opposite directed or oriented. In such a biasing scheme, the magnetic centers of dual sensors self-align each other.
Accordingly, no track-offsetting is needed as disclosed in commonly assigned U.S. Pat. No. 5,783,460 of Han et al. for xe2x80x9cMethod of Making Self-Aligned Dual Stripe MagnetoResistive (DSMR) Head for High Density Recordingxe2x80x9d which shows a DSMR process using a lift off stencil to form a patterned dielectric layer edge. To achieve this quiescent biasing scheme, one can produce both sensors with Anti-Parallel EXchange-biasing (APEX) by means of exchange coupling between Anti-Ferro-Magnetic (AFM) and Ferro-Magnetic (FM) material.
U.S. Pat. No. 5,408,377 of Gurney et al. for xe2x80x9cMagnetoresistive Sensor with Ferromagnetic Sensing Layerxe2x80x9d shows a Ruthenium (Ru) AFM coupling film in a spin valve sensor.
U.S. Pat. No. 5,644,456 of Smith et al. for xe2x80x9cMagnetically Capped Dual Magnetoresistive Reproduce Headxe2x80x9d shows a cap layer in a DSMR that breaks exchange coupling between the magnetically permeable layer and MR elements.
U.S. Pat. No. 5,684,658 of Shi et al. for xe2x80x9cHigh Track Density Dual Stripe Magnetoresistive (DMSR) Headxe2x80x9d shows a DSMR having first and second anti-Ferro-Magnetic longitudinal biasing layers.
U.S. Pat. No. 5,731,936 of Lee et al. for xe2x80x9cMagnetoresistive (MR) Sensor with Coefficient Enhancing that Promotes Thermal Stabilityxe2x80x9d provides chromium based spacer layers for an MR layer of NiCr or NiFeCr compositions in place of Ta spacers to avoid a reported problem of degrading the magnetic moment of the MR stripe when high heat at the interface between the Ta spacer layer and the Permalloy (MR stripe) causing interdiffusion therebetween.
See Parkin, xe2x80x9cSystematic Variation of the Strength and Oscillation Period of Indirect Magnetic Exchange Coupling through the 3d. 4d and 5d Transition Metalsxe2x80x9d, Physical Review Letters Vol. 67, No. 25, pp. 3598-3601 (Dec. 16, 1991)
U.S. Pat. No. 5,766,780 of Huang et al. for xe2x80x9cReversed Order NiMn Exchange Biasing for Dual Magnetoresistive Headsxe2x80x9d teaches a DSMR with a Mo layer as the conductor/seed layer on an alumina base coat. A NiMn exchange bias layer is formed on the Mo layer. A NiFe MR sensor layer is formed on the surface of the NiMn exchange bias layer.
This invention teaches a Ruthenium/Ferro-Magnetic/AFM three layer structure to replace an AFM in a sensor in an MR or DSMR. In the case of a DSMR, when one magnetically aligns both AFM in the same direction, the biasing direction of the MR sensor under the ruthenium will be anti-parallel to the other one. A key element of the invention is the Ru spacer that shows increased coupling strength.
In accordance with this invention a method is provided for forming a longitudinally magnetically biased dual stripe magnetoresistive (DSMR) sensor element comprises forming a first patterned magnetoresistive (MR) layer. Contact the opposite ends of the patterned magnetoresistive (MR) layer with a first pair of stacks defining a track width of the first magnetoresistive (MR) layer, each of the stacks including a first Anti-Ferro-Magnetic (AFM) layer and a first lead layer. Then anneal the device in the presence of a longitudinal external magnetic field. Next, form a second patterned magnetoresistive (MR) layer above the previous structure. Contact the opposite ends of the second patterned magnetoresistive (MR) layer with a second pair of stacks defining a second track width of the second patterned magnetoresistive (MR) layer. Each of the second pair of stacks includes spacer layer composed of a metal, a Ferro-Magnetic (FM) layer, a second Anti-Ferro-Magnetic (AFM) layer and a second lead layer. Then anneal the device in the presence of a second longitudinal external magnetic field.
In accordance with another aspect of this invention, a longitudinally magnetically biased dual stripe magnetoresistive (DSMR) sensor element is provided including a first patterned magnetoresistive (MR) layer. There are a pair of opposite ends of the first patterned MR layer being in contact with a first pair of stacks defining a first track width of the patterned MR layer. Each of the stacks includes a first AFM layer and a first lead layer. The device has a first longitudinal magnetic field bias in the first AFM layer. There is a second patterned MR layer contacted at its opposite ends by a second pair of stacks defining a second track width of the second patterned MR layer. Each of the second pair of stacks includes a spacer layer composed of a metal, a Ferro-Magnetic (FM) layer, a second AFM layer and a second lead layer. The device has a second longitudinal magnetic field bias in the second AFM layer. Preferably, the spacer layer is composed of a metal selected from the group consisting of ruthenium (Ru), rhodium (Rh), copper (Cu) and chromium (Cr). It is also preferred that the Ferro-Magnetic layers are composed of a metal selected from the group consisting of NiFe, Co, Fe, NiCo and CoFe. Moreover, it is preferred that the AFM layers are composed of a metal selected from the group consisting of IrMn, NiMn, PtMn, PdPtMn and FeMn.